Milieu is the representation of an indefinitely extendible line or plane, at once continuous and homogenous, and with neither definite shape nor privileged position, prevailed over the representation of a sphere or circle, attached to a fixed center of reference -- milieu does not evoke any relation except that of a position endlessly negated by exteriority.
Milieu is both the environment within which actions take place and the material on which actions operate.
Milieu is, in a mechanistic view, the idea that it is the river that makes fishes lead their lives just how they lead it, such that they are persons without personality.
Milieu is put in poetic terms, the idea that, following condillac's fable of the statue, 'when the air smells like roses, a statue is rose-scented'.
Milieu is the environment within which actions take place and also the material on which action operates.